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Differences in Physical-Chemical Properties of the Nonprinting Areas for Conventional and CtP Process

The difference between printing and nonprinting areas in lithography is achieved through opposite physical-chemical properties. The printing areas attract hydrophobic substances – printing inks. The nonprinting areas, made of aluminum-oxide, attract hydrophilic substances – the fountain solution. In the printing process, the nonprinting areas are first covered with fountain solution, which makes them unable to adsorb printing ink. The amount and stability of the fountain solution adsorption on those areas has direct influence on the quality level of the reproduction. The aim of this paper was to determine how developing time in conventional and CtP plate printing processes influences the physical- chemical properties of the nonprinting areas. Therefore, samples of conventional and CtP printing plate were lightened in optimal time and then developed in various times. The contact angle between wetting solution and nonprinting areas was measured. Results have shown differences in physical-chemical properties between those two types of plates.

Plate making process; conventional process; CtP process; developing time; contact angle

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